Clearer weather finally allowed Indonesian helicopters to land and retrieve some remains of the 45 people aboard a Russian-made plane that crashed into a volcano during a demonstration flight.

Investigators still have found no sign of the black box recorder that might explain why the new Sukhoi Superjet-100 slammed into Mount Salak about halfway through a 50-minute flight intended to woo potential Indonesian airline buyers on Wednesday.

Search teams who climbed the dormant volcano's near-vertical slopes have been struggling to retrieve remains of the victims, and helicopters were unable to land because of thick fog shrouding the mountain about 80 kilometres southwest of Jakarta, the capital. All those aboard the flight are now presumed dead, and the plane's shredded wreckage is scattered around the dense jungle.

"We also have deployed a team to find the black box, but so far it had yet found," Prakoso said.

Col. Anton Chastila, a police forensic doctor in Jakarta, said his team has received the remains, adding it was unclear how many victims they represent.

About 60 forensic experts will sort through the body parts piece by piece and take DNA samples to identify them, Chastila said.

Wednesday's demonstration — locally known as a "joy flight" — was mostly carrying representatives from Indonesian airlines, which are rapidly expanding to serve a burgeoning middle class in the sprawling archipelago where air travel between islands is a quicker alternative to ferries.

Just 21 minutes after takeoff from a Jakarta airfield, the Russian pilot and co-pilot asked for permission to drop from 3,000 metres to 1,800 metres. They gave no explanation, disappearing from the radar immediately afterward.

It was not clear why the crew asked to shift course, especially since they were so close to the 2,200-metre volcano, officials have said.

The Superjet is Russia's first new model of passenger jet since the fall of the Soviet Union two decades ago and was intended to help resurrect its aerospace industry.